This invention relates to optical target detection systems and in particular to infra-red optical detection systems.
The invention seeks to provide improved such systems.
According to this invention, an optical target detection system comprises means for causing an array of optical detectors to scan across a field of view in swathes in one co-ordinate direction, means for scanning said field of view in another co-ordinate direction, means for producing target responses resulting from scanning in said one co-ordinate direction, means for generating an address code related to the position in said one co-ordinate direction at which a detection occurs, first storage means for storing said address code, means for producing target responses resulting from scanning in the other co-ordinate direction, means for generating an address code related to the position in said other co-ordinate direction at which a detection occurs, second storage means for storing said last mentioned address code and means for reading out said first and second stores if a detection resulting from said scanning in said one co-ordinate direction corresponds to a detection resulting from said scanning in said other co-ordinate direction.
Preferably said system is an infra-red target detection system, said detectors being infra-red detectors.
Preferably said means for scanning said field of view in said other co-ordinate direction comprises means for sequentially sampling the outputs of the detector elements in said array in synchronism with said scanning in said one co-ordinate direction.
Preferably said one co-ordinate direction is the vertical and said other co-ordinate direction is the horizontal.
Preferably a third store is provided to store the first and last mentioned address codes of a target when said first and second storage means are read out.
Preferably for each of the detector elements in said array an individual processing channel is provided for processing target detectors occurring during scanning of that detector in its swathe in said one co-ordinate direction, each of said last mentioned channels comprising an individual address store for storing code words related to the position in which in said one co-ordinate direction the respective individual detector element detects a target, said last mentioned individual store forming part of said first storage means, gating means for controlling the reading out of said individual stores, a pulse detector connected to the output of said individual detector element and arranged to provide an output indicative of the instant of target detection by said individual detector element, which output is connected to control the loading of said individual store with an address code, a pulse output indicative of a target detection and an analogue waveform output corresponding to the input of said individual pulse detector, all of said last mentioned outputs from said individual pulse detector being synchronised to the corresponding outputs of the individual processing channels provided in respect of the other individual detector elements of the array.
Preferably a common processing channel is provided for processing target responses resulting from scanning in said other co-ordinate direction and last mentioned processing channel including a further pulse detector to which the combined analogue waveform outputs of all of said individual processing channels for target responses resulting from scanning in said one co-ordinate direction are applied in combination (preferably via a low pulse filter arrangement) and said last mentioned pulse detector providing two synchronised outputs the first of which relates to the instant at which a pulse is detected and the other of which comprising a control pulse generated upon target detection, said last mentioned pulse being arranged to be gated under the control of the corresponding pulses generated by the pulse detectors in the processing channels provided to process target responses resulting from scanning in said one direction whereby said control pulse output is only provided if a detection resulting from said scanning in said one co-ordinate direction corresponds to a detection resulting from said scanning in said other co-ordinate direction, means for utilising said signal representing the instant of detection for loading said second storage means consisting of a common address store and means for utilising said output control pulse to control the transfer of address codes stored in said first and second stores to said third store.
Typically the number of detector elements in said array is twenty-nine, said address code relating to the position in said one co-ordinate direction at which a detection occurs is a nine-bit code word and said address code related to the position in said other co-ordinate direction at which a detection occurs is a seven-bit code word.